Effect of combined high-temperature and UV-C radiation on stilbene accumulation and stilbene biosynthetic pathway genes in mulberry ( Morus sp.)

Resveratrol (Res) and oxyresveratrol (Oxyres), stilbene compounds found in several plants, have gained much attention due to their critical roles in human health through their antioxidants, anti-cancer, and antibacterial effects. Res and Oxyres are, however, only found in trace amounts during natural growing conditions. Different biotechnological strategies, including elicitation, have been used to enhance Res and Oxyres. Therefore, this study aimed to characterize the stilbene synthase ( STS ) gene involved in Res biosynthesis from mulberry and investigate the effects of combined stress on Res and Oxyres contents. The result showed that the STS gene consists of 1176 bp, encoding 391 amino acid residues with an estimated molecular mass and a theoretical pI of 42.68 kDa and 6.15, respectively. The effects of high temperature (40 °C, 12 h), UV-C (50 kJ m −2 , 15 min), and combined stress of high temperature (HT) followed by UV-C were investigated for Res and Oxyres accumulation in the callus culture of mulberry. The contents of Res and Oxyres were significantly enhanced to 33.84 and 39.08 µgg −1 DW, respectively, in response to HT. UV-C significantly increased Oxyres content to 36.6 µg g −1 DW compared to the untreated condition. Interestingly, HT and UV-C synergistically enhanced Oxyres, reaching 81 µg g −1 DW, the highest accumulation. Furthermore, the stilbene biosynthesis-related gene expressions were examined using qRT-PCR. The result revealed that the PAL , 4CL , STS , and CHS expressions were upregulated in response to UV-C and combined stress conditions. The findings of this study demonstrated that the effects of HT and UV-C could potentially enhance the production of Res and Oxyres in mulberries.